It has long been known that headsets for two-way voice communication can advantageously be constructed from small, lightweight components, such that the overall weight of the headset may be on the order of one ounce. For example, U.S. Pat. No. 3,184,556, issued May 18, 1965, to W. K. Larkin, discloses a miniaturized headset wherein a hearing-aid size microphone transducer and a similarly miniaturized transducer are placed in a capsule mounted near the user's ear; speech is conducted to the microphone via an acoustic tube positioned near the user's mouth, while incoming communications emanating from the receiver are conducted to the user's ear via a second acoustic tube. Larkin-type headsets have been used with either a light headband or the temple bar of an eyeglass frame as the supporting member for the transducer housing.
In order to eliminate the necessity for having a headband or an eyeglass frame to support the transducer housing, various headsets have employed the so-called "post-auricle" configuration, wherein the transducers are placed in a capsule which is mounted behind the ear of the user, and is shaped to fit generally along the saddle area behind the ear. For example, U.S. Pat. No. 3,548,118, issued Dec. 15, 1970, to K. J. Hutchings, discloses such a post-auricle arrangement, with an acoustic voice tube passing over the ear and into the headset capsule, and an acoustic ear tube passing from the capsule under the wearer's ear and up into the ear canal. The arrangement disclosed in the Hutchings patent is embodied in a headset commercially sold by Plantronics, Inc., the assignee of the present application, under its trademark "StarSet."
It has also been known to provide a headset having a capsule shape generally similar to that disclosed in the above-identified Hutchings patent, but not employing an acoustic voice tube. Instead, an electret-type microphone is mounted at the end of a swivelable boom, so that it can be positioned near the wearer's mouth. The boom is hollow, and electrical lead wires are passed from the electret microphone through the boom and into the headset capsule, where they are incorporated into the main headset cable, which in turn is plugged into a switchboard or other means of connecton to a telephone line. An example of this boomelectret microphone arrangement is found in the headset commercially offered by Northern Electric Company under its trademark "Venture."
The aforementioned headset designs, and all other post-auricle headset designs known to applicants, have attempted to provide stability by means of the judicious location of the acoustic voice tube or boom; or by means of the anchoring effect of the acoustic ear tube; or by attempting to make the saddle curvature of the headset capsule fit as many human ears as possible. Until the present invention, shaping of other portions of the headset capsule was limited to efforts to contain the transducers adequately, and to make the top-most portion of the capsule as thin as possible, thereby to provide adequate mounting space for the headset to pass over the top of the ear, where the distance between the auricle and the skull is usually small, especially if the user is wearing eyeglasses.
Headset design is primarily a subjective human engineering problem, with very few workable theoretical guide lines. Proposed designs generally need to be tried out on many differnt people of varying heights, weights, ages, head shapes, etc., to determine their reactions with regard to comfort, stability, and acoustic properties.